The quality and depth of road and footway surfacing plays an important role in safety for the road and pathway users. Partial subsidence or rucking of the surfacing material may trip a pedestrian on a footway or deflect the tyres of a road vehicle risking loss of control by the motorist.
Highways legislation covering the mandatory requirements for road and pavement quality and particularly depth of surfacing layers has tightened up considerably over recent years. Under the New Roads and Street Works Act, 1991 the allowed tolerance for thickness of upper surfacing layer or “wearing course” is to be within +10 mm to −5 mm of a specified thickness for a given material—most commonly 40 mm. Very substantial penalties are exacted for failure to meet this requirement.
Through safety consciousness and the impact of the stringent legal obligations, those whose work entails excavating roads and pathways are obliged to take great care when reinstating those roads or pathways and are subject to official inspection of their reinstatement work. In the case, for example, of cable television engineers who routinely channel through hundreds of miles of roads and footways to provide cable access to millions of consumers there is a very major budgetary burden to ensure that the roads and footways are properly reinstated and failure to meet the statutory requirement for surfacing layer thickness on inspection can greatly increase their operating costs. Accordingly, it is very important to them to have a demonstrably precise and reliable gauge for measuring the thickness of core samples taken for inspection.
Conventionally, the core samples for inspection are extracted from the site as vertical cylinders of the bound material generally between 100 mm and 150 mm in diameter and up to 300 mm in depth although generally the most important portion to be measured, the wearing course, constitutes only the first 40 mm or so. The core samples are sent to a government laboratory for measurement, taking days and weeks to process and removing any opportunity for witnessing or validation of the results. GB-A-2326722 discloses a bound materials core measuring device comprising a free-standing, rigid, transparent or apertured tubular body adapted to accommodate a core sample of road or pathway surfacing bound material and having a plurality of graduated scales extending therealong at spaced intervals therearound so as to enable the sample to be viewed through the body and the depth of the relevant one or more layers of the core sample to be measured from a plurality of angles by reading from each of the plurality of graduated scales.
The device disclosed in GB-A-2326722 has a plurality of fins extending across the tubular body which support any core sample held within the tubular body. The use of fin supports enable debris to drop away from beneath the core sample resting at the bottom of the tubular body to eliminate associated measurement errors. The fins serve also as support legs for the tubular body which extend from within the tubular body to the exterior thereof.
The baseline zero of the graduated scales is at the level on the tubular body at which a core sample comes to rest when placed in the tubular body. The fin legs are suitably adjustable to ensure that they are level with the baseline zero level before measuring commences.